Valve prosthesis for implantation in body channels

ABSTRACT

A valve prosthesis which is especially useful in the case of aortic stenosis and capable of resisting the powerful recoil force and to stand the forceful balloon inflation performed to deploy the valve and to embed it in the aortic annulus, comprises a collapsible valvular structure and an expandable frame on which said valvular structure is mounted. The valvular structure is composed of physiologically compatible valvular tissue that is sufficiently supple and resistant to allow the valvular structure to be deformed from a closed state to an opened state. The valvular tissue forms a continuous surface and is provided with strut members that create stiffened zones which induce the valvular structure to follow a patterned movement in its expansion to its opened state and in its turning back to its closed state.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 10/139,741, filed May 2, 2002, which is a continuation ofco-pending U.S. patent application Ser. No. 09/795,803, filed Feb. 28,2001, now abandoned, which in turn is a continuation of U.S. patentapplication Ser. No. 09/345,824, filed Jun. 30, 1999, now abandoned,which is a National Phase filing of PCT patent application No. PCT/EP97/07337, filed Dec. 31, 1997 and designating the United States, all ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a valve prosthesis for implantation inbody channels, more particularly but not only to, cardiac valveprosthesis to be implanted by a transcutaneous catheterizationtechnique.

The valve prosthesis can be also applied to other body channels providedwith native valves, such as veins or in organs (liver, intestine,urethra . . . ).

The present invention also relates to a method for implanting a valveprosthesis, such as the valve according to the present invention.

Implantable valves, which will be indifferently designated hereafter as“IV”, “valve prosthesis” or “prosthetic valve”, permits the reparationof a valvular defect by a less invasive technique in place of the usualsurgical valve implantation which, in the case of valvular heartdiseases, requires thoracotomy and extracorporeal circulation. Aparticular use for the IV concerns patients who cannot be operated onbecause of an associated disease or because of very old age or alsopatients who could be operated on but only at a very high risk.

Although the IV of the present invention and the process for implantingsaid IV can be used in various heart valve diseases, the followingdescription will first concern the aortic orifice in aortic stenosis,more particularly in its degenerative form in elderly patients.

Aortic stenosis is a disease of the aortic valve in the left ventricleof the heart. The aortic valvular orifice is normally capable of openingduring systole up to 4 to 6 cm², therefore allowing free ejection of theventricular blood volume into the aorta. This aortic valvular orificecan become tightly stenosed, and therefore the blood cannot anymore befreely ejected from the left ventricle. In fact, only a reduced amountof blood can be ejected by the left ventricle which has to markedlyincrease the intra-cavitary pressure to force the stenosed aorticorifice. In such aortic diseases, the patients can have syncope, chestpain, and mainly difficulty in breathing. The evolution of such adisease is disastrous when symptoms of cardiac failure appear, since 50%of the patients die in the year following the first symptoms of thedisease.

The only commonly available treatment is the replacement of the stenosedaortic valve by a prosthetic valve via surgery: this treatment moreoverproviding excellent results. If surgery is impossible to perform, i.e.,if the patient is deemed inoperable or operable only at a too highsurgical risk, an alternative possibility is to dilate the valve with aballoon catheter to enlarge the aortic orifice. Unfortunately, a goodresult is obtained only in about half of the cases and there is a highrestenosis rate, i.e., about 80% after one year.

Aortic stenosis is a very common disease in people above seventy yearsold and occurs more and more frequently as the subject gets older. Asevidenced, the present tendency of the general evolution of thepopulation is becoming older and older. Also, it can be evaluated, as acrude estimation, that about 30 to 50% of the subjects who are olderthan 80 years and have a tight aortic stenosis, either cannot beoperated on for aortic valve replacement with a reasonable surgical riskor even cannot be considered at all for surgery.

It can be estimated that, about 30 to 40 persons out of a million peryear, could benefit from an implantable aortic valve positioned by acatheterization technique. Until now, the implantation of a valveprosthesis for the treatment of aortic stenosis is consideredunrealistic to perform since it is deemed difficult to superpose anothervalve such an implantable valve on the distorted stenosed native valvewithout excising the latter.

From 1985, the technique of aortic valvuloplasty with a balloon catheterhas been introduced for the treatment of subjects in whom surgery cannotbe performed at all or which could be performed only with a prohibitivesurgical risk. Despite the considerable deformation of the stenosedaortic valve, commonly with marked calcification, it is often possibleto enlarge significantly the aortic orifice by balloon inflation, aprocedure which is considered as low risk.

However, this technique has been abandoned by most physicians because ofthe very high restenosis rate which occurs in about 80% of the patientswithin 10 to 12 months. Indeed, immediately after deflation of theballoon, a strong recoil phenomenon often produces a loss of half oreven two thirds of the opening area obtained by the inflated balloon.For instance, inflation of a 20 mm diameter balloon in a stenosed aorticorifice of 0.5 cm² area gives, when forcefully and fully inflated, anopening area equal to the cross sectional area of the maximally inflatedballoon, i.e., about 3 cm². However, measurements performed a fewminutes after deflation and removal of the balloon have only an areaaround 1 cm² to 1.2 cm². This is due to the considerable recoil of thefibrous tissue of the diseased valve. The drawback in this procedure hasalso been clearly shown on fresh post mortem specimens.

However, it is important to note that whereas the natural normal aorticvalve is able to open with an orifice of about 5 to 6 cm² and toaccommodate a blood flow of more that 15 l/min. during heavy exercisefor instance, an opening area of about 1.5 to 2 cm² can accept a 6 to 8l/min blood flow without a significant pressure gradient. Such a flowcorresponds to the cardiac output of the elderly subject with limitedphysical activity.

Therefore, an IV would not have to produce a large opening of the aorticorifice since an opening about 2 cm² would be sufficient in mostsubjects, in particular in elderly subjects, whose cardiac outputprobably does not reach more than 6 to 8 l/min. during normal physicalactivity. For instance, the surgically implanted mechanical valves havean opening area which is far from the natural valve opening that rangesfrom 2 to 2.5 cm², mainly because of the room taken by the largecircular structure supporting the valvular part of the device.

The prior art describes examples of cardiac valves prosthesis that areaimed at being implanted without surgical intervention by way ofcatheterization. For instance, U.S. Pat. No. 5,411,552 describes acollapsible valve able to be introduced in the body in a compressedpresentation and expanded in the right position by balloon inflation.

Such valves, with a semi-lunar leaflet design, tend to imitate thenatural valve. However, this type of design is inherently fragile, andsuch structures are not strong enough to be used in the case of aorticstenosis because of the strong recoil that will distort this weakstructure and because they would not be able to resist the ballooninflation performed to position the implantable valve. Furthermore, thisvalvular structure is attached to a metallic frame of thin wires thatwill not be able to be tightly secured against the valve annulus. Themetallic frame of this implantable valve is made of thin wires like instents, which are implanted in vessels after balloon dilatation. Such alight stent structure is too weak to allow the implantable valve to beforcefully embedded into the aortic annulus. Moreover, there is a highrisk of massive regurgitation (during the diastolic phase) through thespaces between the frame wires which is another prohibitive risk thatwould make this implantable valve impossible to use in clinicalpractice.

Furthermore, an important point in view of the development of the IV isthat it is possible to maximally inflate a balloon placed inside thecompressed implantable valve to expand it and insert it in the stenosedaortic valve up to about 20 to 23 mm in diameter. At the time of maximumballoon inflation, the balloon is absolutely stiff and cylindricalwithout any waist. At that moment, the implantable valve is squeezed andcrushed between the strong aortic annulus and the rigid balloon with therisk of causing irreversible damage to the valvular structure of theimplantable valve.

SUMMARY OF THE INVENTION

The invention is aimed to overcome these drawbacks and to implant an IVwhich will remain reliable for years.

A particular aim of the present invention is to provide an IV,especially aimed at being used in case of aortic stenosis, whichstructure is capable of resisting the powerful recoil force and to standthe forceful balloon inflation performed to deploy the IV and to embedit in the aortic annulus.

Another aim of the present invention is to provide an efficientprosthesis valve which can be implanted by a catheterization technique,in particular in a stenosed aortic orifice, taking advantage of thestrong structure made of the distorted stenosed valve and of the largeopening area produced by preliminary balloon inflation, performed as aninitial step of the procedure.

A further aim of the present invention is to provide an implantablevalve which would not produce any risk of fluid regurgitation.

A further aim of the present invention is to provide a valve prosthesisimplantation technique using a two-balloon catheter and a two-framedevice.

These aims are achieved according to the present invention whichprovides a valve prosthesis of the type mentioned in the introductorypart and wherein said valve prosthesis comprises a collapsiblecontinuous structure with guiding means providing stiffness and a frameto which said structure is fastened, said frame being strong enough toresist the recoil phenomenon of the fibrous tissue of the diseasedvalve.

The IV, which is strongly embedded, enables the implantable valve to bemaintained in the right position without any risk of furtherdisplacement, which would be a catastrophic event.

More precisely, this valvular structure comprises a valvular tissuecompatible with the human body and blood, which is supple and resistantto allow said valvular structure to pass from a closed state to an openstate to allow a body fluid, more particularly the blood, exertingpressure on said valvular structure, to flow. The valvular tissue formsa continuous surface and is provided with guiding means formed orincorporated within, creating stiffened zones which induce the valvularstructure to follow a patterned movement from its open position to itsclosed state and vice-versa, providing therefore a structuresufficiently rigid to prevent diversion, in particular into the leftventricle and thus preventing any regurgitation of blood into the leftventricle in case of aortic implantation.

Moreover, the guided structure of the IV of the invention allows thetissue of this structure to open and close with the same patternedmovement while occupying as little space as possible in the closed stateof the valve. Therefore, owing to these guiding means, the valvularstructure withstands the unceasing movements under blood pressurechanges during the heart beats.

More preferably, the valvular structure has a substantially truncatedhyperboloidal shape in its expanded position, with a larger base and agrowing closer neck, ending in a smaller extremity forming the upperpart of the valvular structure. The valvular structure has a curvatureat its surface that is concave towards the aortic wall. Such a shapeproduces a strong and efficient structure in view of thesystolo-diastolic movement of the valvular tissue. Such a valvularstructure with its simple and regular shape also lowers the risk ofbeing damaged by forceful balloon inflation at the time of IVdeployment.

A trunco-hyperboloidal shape with a small diameter at the upperextremity facilitates the closure of the valve at the beginning ofdiastole in initiating the starting of the reverse movement of thevalvular tissue towards its base. Another advantage of this truncatedhyperboloidal shape is that the upper extremity of the valvularstructure, because of its smaller diameter, remains at a distance fromthe coronary ostia during systole as well as during diastole, thusoffering an additional security to ensure not to impede at all thepassage of blood from the aorta to the coronary ostia.

As another advantageous embodiment of the invention, the guiding meansof the valvular structure are inclined strips from the base to the upperextremity of the valvular structure with regard to the central axis ofthe valvular structure. This inclination initiates and imparts a generalhelicoidal movement of the valvular structure around said central axisat the time of closure or opening of said structure, such a movementenabling to help initiate and finalize the closure of the valvularstructure. In particular, this movement improves the collapse of thevalvular structure towards its base at the time of diastole and duringthe reversal of flow at the very beginning of diastole. During diastole,the valvular structure thus fails down, folding on itself and collapseson its base, therefore closing the aortic orifice. The strips can bepleats, strengthening struts or thickened zones.

In other embodiments, said guiding means are rectilinear strips from thebase to the upper extremity of the valvular structure. In this case, theguiding means can comprise pleats, struts or thickened zones. In aparticular embodiment, the stiffened zones then created can beadvantageously two main portions, trapezoidal in shape, formedsymmetrically one to each other with regard to the central axis of thevalvular structure, and two less rigid portions separating said two mainportions to lead to a tight closeness in shape of a closed slot at thetime of closure of the upper extremities of the main portions of thevalvular structure. The thickened zones can be extended up to form thestiffened zones.

More particularly, each of said main slightly rigid portions occupyapproximately one third of the circumference of the valvular structurewhen this latter is in its open position. The slightly rigid portionsmaintain the valvular structure closed during diastole by firmlyapplying themselves on each other. The closure of the valvular structureat the time of diastole thus does not have any tendency to collapse toomuch towards the aortic annulus.

Preferably, the guiding means are a number of pleats formed within thetissue by folding, or formed by recesses or grooves made in the tissue.The shape of the pleats is adapted to achieve a global shape of thedesired type for said position.

Alternatively, the guiding means are made of strengthening struts,preferably at least three, incorporated in the tissue in combination ornot with said pleats.

The guiding means and, in particular, the strengthening struts, help toprevent the valvular tissue from collapsing back too much and to reverseinside the left ventricle through the base of the frame, preventing therisk of blood regurgitation.

In a preferred prosthetic valve of the invention, said valvular tissueis made of synthetic biocompatible material such as TEFLON® or DACRON®,polyethylene, polyamide, or made of biological material such aspericardium, porcine leaflets and the like. These materials are commonlyused in cardiac surgery and are quite resistant, particularly to foldingmovements due to the increasing systolo-diastolic movements of thevalvular tissue and particularly at the junction with the frame of theimplantable valve.

The valvular structure is fastened along a substantial portion of anexpandable frame, by sewing, by molding or by gluing to exhibit atightness sufficiently hermetical to prevent any regurgitation of saidbody fluid between the frame and the valvular structure.

Preferably, an internal cover is coupled or is integral to the valvularstructure and placed between said valvular structure and the internalwall of the frame to prevent any passage of the body fluid through saidframe. Therefore, there is no regurgitation of blood as it would be thecase if there were any space between the valvular structure fastened onthe frame and the zone of application of the frame on the aorticannulus. The internal cover makes a sort of “sleeve” at least below thefastening of the valvular structure covering the internal surface of theframe and thus prevents any regurgitation of blood through the frame.

In the present invention, the frame is a substantially cylindricalstructure capable of maintaining said body channel open in its expandedstate and supporting said collapsible valvular structure.

In a preferred embodiment of the invention, the frame is made of amaterial which is distinguishable from biological tissue to be easilyvisible by non invasive imaging techniques.

Preferably, said frame is a stainless metal structure or a foldableplastic material, made of intercrossing, preferably with rounded andsmooth linear bars. This frame is strong enough to resist the recoilphenomenon of the fibrous tissue of the diseased valve. The size of thebars and their number are determined to give both the maximal rigiditywhen said frame is expanded and the smallest volume when the frame iscompressed.

More preferably, the frame has projecting curved extremities andpresents a concave shape. This is aimed at reinforcing the embedding andthe locking of the implantable valve in the distorted aortic orifice.

In a preferred embodiment of the present invention, the IV is made intwo parts, a first reinforced frame coupled with a second frame which ismade of thinner bars than said first frame and which is embedded insidethe second frame. This second frame to which the valvular structure isfastened as described above, is preferably less bulky than the firstframe to occupy as little space as possible and to be easily expandedusing low pressure balloon inflation.

The present invention also relates to a double balloon catheter toseparately position the first frame in the dilated stenosed aortic valveand place the second frame that comprises the valvular structure. Thiscatheter comprises two balloons fixed on a catheter shaft and separatedby few centimeters.

The first balloon is of the type sufficiently strong to avoid burstingeven at a very high pressure inflation and is aimed at carrying, in itsdeflated state, a strong frame aimed at scaffolding the previouslydilated stenosed aortic valve. The second balloon is aimed at carryingthe second frame with the valvular structure.

An advantage of this double balloon catheter is that each balloon has anexternal diameter which is smaller than known balloons since eachelement to be expanded is smaller.

Moreover, such a double balloon catheter allows to enlarge the choicefor making an efficient valvular structure enabling to overcome thefollowing two contradictory conditions:

-   -   1) having a soft and mobile valvular structure capable of        opening and closing freely in the blood stream, without risk of        being damaged by balloon inflation; and    -   2) needing a very strong structure able to resist the recoil        force of the stenosed valve and capable of resisting, without        any damage, a strong pressure inflation of the expanding        balloon.

Furthermore, the shaft of said double balloon catheter comprises twolumens for successive and separate inflation of each balloon. Of note,an additional lumen capable of allowing a rapid inflation takesadditional room in the shaft.

The invention also relates to a method of using a two-balloon catheterwith a first frame and second frame to which a valve prosthesis of thetype previously described is fastened.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained and other advantages and featureswill appear with reference to the accompanying schematical drawingswherein:

FIGS. 1 a, 1 b and 1 c illustrate, in section views, respectively, thenormal aortic valve in systole, in diastole and a stenosed aortic valve;

FIGS. 2 a and 2 b illustrate two examples of a metallic frame which arecombined to a valvular structure according to the present invention;

FIGS. 3 a and 3 b illustrate a frame according to the invention in itsexpanded position with an opening out of the extremities, respectively,with a cylindrical and a concave shape;

FIGS. 4 a and 4 b illustrate an IV of the invention respectively in itscompressed position and in its expanded position in an open position asin systole;

FIGS. 5 a and 5 b illustrate respectively an IV of the invention in itsclosed position and a sectional view according to the central axis ofsuch a valvular structure which is closed as in diastole;

FIGS. 6 a to 6 d illustrate a sectional view according to the centralaxis of an IV according to the present invention and showing theinternal cover and the external cover of the valvular structureoverlapping partially or non overlapping the frame bars;

FIG. 7 illustrates the frontal zig-zag fastening line of the valvulartissue on the frame;

FIGS. 8 a and 8 b illustrate, respectively, a perspective view of avalvular structure and an internal cover made all of one piece and aperspective view of the corresponding frame into which they will beinserted and fastened;

FIGS. 9 a and 9 b illustrate inclined strengthening struts, an exampleof a valvular structure according to the invention, respectively in theopen position and in the closed position;

FIGS. 10 a and 10 b illustrate an example of a valvular structurecomprising pleats, respectively in the open and in the closed position;

FIGS. 11 a and 11 b illustrate a valvular structure comprising twotrapezoidal slightly rigid portions, respectively in the open and in theclosed position;

FIGS. 11 c to 11 e illustrate a valvular structure comprising arectangular stiffened zone, respectively in the open, intermediate andclosed position;

FIGS. 12 a and 12 b illustrate, respectively, a perspective and crosssectional views of an implantable valve in its compressed presentationsqueezed on a balloon catheter;

FIGS. 13 a to 13 l illustrate views of the successive procedure stepsfor the IV implantation in a stenosed aortic orifice;

FIG. 14 illustrates an implantable valve made in two parts in itscompressed presentation squeezed on a two-balloon catheter with areinforced frame on a first balloon and with the implantable valve onthe second balloon; and

FIGS. 15 a to 15 f illustrate the successive steps of the implantationof the implantation valve in two parts with a two-balloon catheter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the diastole and systole illustrations of section views of FIGS. 1 aand 1 b, the arrows A indicates the general direction of the blood flow.The semi-lunar leaflets 1 and 2 of a native aortic valve (with only twoout of three shown here) are thin, supple and move easily from thecompletely open position (systole) to the closed position (diastole).The leaflets originate from an aortic annulus 2 a.

The leaflets 1′ and 2′ of a stenosed valve as illustrated in FIG. 1 c,are thickened, distorted, calcified and more or less fused, leaving onlya small hole or a narrow slit 3, which makes the ejection of blood fromthe left ventricle cavity 4 into the aorta 5 difficult and limited.FIGS. 1 a to 1 c show also the coronary artery ostium 6 a and 6 b andFIG. 1 a shows, in particular, the mitral valve 7 of the left ventriclecavity 4.

An implantable valve according to the invention essentially comprises asupple valvular structure supported by a strong frame. The positioningof the implantable valve is an important point since the expanded framehas to be positioned exactly at the level of the native valvularleaflets 1, 2 of the native valve, the structures of which are pushedaside by the inflated balloon.

Ideally, the implantable valve is positioned with the fastening line ofthe valvular structure on the frame exactly on the remains of thecrushed stenosed valve to prevent any regurgitation of blood. Inpractice, it is difficult to position the implantable valve within lessthan 2 or 3 mm. However, any risk of regurgitation of blood iseliminated with the presence of an internal cover, as will be describedbelow.

The upper limit of the frame should be placed below the opening of thecoronary arteries, i.e., the coronary ostia 6, or at their level so thatthe frame does not impede free blood flow in the coronary arteries. Thispoint is a delicate part of positioning an IV since the distance betweenthe superior limit of the leaflets of the natural valve and the coronaryostia 6 is only about 5 to 6 mm. However, the ostia are located in theValsalva sinus 8 which constitutes a hollow that are located a littleout of the way. This helps to prevent from impeding the coronary bloodflow by the IV.

At the time of implantation, the operator evaluates the exactpositioning of the coronary ostia by looking at the image produced by asus-valvular angiogram with contrast injection performed before theimplantation procedure. This image will be fixed in the same projectionon a satellite TV screen and will permit the evaluation of the level ofthe origin of the right and left coronary arteries. Possibly, in casethe ostia are not clearly seen by sus-valvular angiography, a thin guidewire, as those used in coronary angioplasty, is positioned in each ofthe coronary arteries to serve as a marker of the coronary ostia.

The lower part of the frame of the IV preferably extends by 2 or 3 mminside the left ventricle 4, below the aortic annulus 2 a. However, thispart of the frame should not reach the insertion of the septal leafletof the mitral valve 7, so that it does not interfere with its movements,particularly during diastole.

FIGS. 2 a and 2 b show respectively an example of a cylindrical frame orstent 10 comprising intercrossing linear bars 11, with two intersectionsI by bar 11, the bars 11 being soldered or provided from a folded wireto constitute the frame, with for instance a 20 mm, 15 mm or 12 mmheight, and an example with only one intersection of bars 11.Preferably, such a frame is expandable from a size of about 4 to 5millimeters to a size of about 20 to 25 mm in diameter, or even to about30-35 mm (or more) in particular cases, for instance for the mitralvalve. Moreover, said frame, in its fully expanded state, has a heightof approximately between 10 and 15 mm and in its fully compressed frame,a height of approximately 20 mm. The number and the size of the bars areadapted to be sufficiently strong and rigid when the frame is fully openin the aortic orifice to resist the strong recoil force exerted by thedistorted stenosed aortic orifice after deflation′ of the balloon usedin the catheterization technique which has been previously maximallyinflated to enlarge the stenosed valve orifice.

The frame may have several configurations according to the number ofbars 11 and intersections. This number, as well as the size and thestrength of the bars 11, are calculated taking into account all therequirements described, i.e., a small size in its compressed form, itscapacity to be enlarged up to at least 20 mm in diameter and beingstrong when positioned in the aortic orifice to be able to be forcefullyembedded in the remains of the diseased aortic valve and to resist therecoil force of the aortic annulus. The diameter of the bars is chosen,for instance, in the range of 0.1-0.6 mm.

A frame particularly advantageous presents, when deployed in itsexpanded state, an opening out 12 at both extremities as shown in FIGS.3 a and 3 b, the frame having a linear profile (FIG. 3 a) or a concaveshape profile (FIG. 3 b). This is aimed at reinforcing the embedding ofthe IV in the aortic orifice. However, the free extremities of theopenings 12 are rounded and very smooth to avoid any traumatism of theaorta or of the myocardium.

The structure of a preferred frame used in the present invention bothmaintains the aortic orifice fully open once dilated and produces asupport for the valvular structure. The frame is also foldable. Whenfolded by compression, the diameter of said frame is about 4 to 5millimeters, in view of its transcutaneous introduction in the femoralartery through an arterial sheath of 14 to 16 F (F means French, a unitusually used in cardiology field) i.e., about 4.5 to 5.1 mm. Also, asdescribed below, when positioned in the aortic orifice, the frame isable to expand under the force of an inflated balloon up to a size of 20to 23 mm in diameter.

The frame is preferably a metallic frame, preferably made of steel. Itconstitutes a frame with a grate type design able to support thevalvular structure and to behave as a strong scaffold for the openstenosed aortic orifice.

When the frame is fully expanded, its intercrossing bars push againstthe remains of the native stenosed valve that has been crushed asideagainst the aortic annulus by the inflated balloon. This produces apenetration and embeds the bars within the remains of the stenosedvalve, in particular owing to a concave profile of the frame providedwith an opening out, as illustrated in FIG. 3 b. This embedding of theframe on the aortic annulus, or more precisely on the remains of thecrushed distorted aortic valve, will be determinant for the strongfixation of the IV in the right position, without any risk ofdisplacement.

Moreover, the fact that the valve leaflets in degenerative aorticstenosis are grossly distorted and calcified, sometimes leaving only asmall hole or a small slit in the middle of the orifice, has to beconsidered an advantage for the implantation of the valve and for itsstable positioning without risk of later mobilization. The fibrous andcalcified structure of the distorted valve provides a strong base forthe frame of the IV and the powerful recoil phenomenon that results fromelasticity of the tissues contribute to the fixation of the metallicframe.

The height of the fully expanded frame of the illustrated frames 10 ispreferably between 10 and 15 mm. Indeed, since the passage from thecompressed state to the expanded state results in a shortening of themetallic structure, the structure in its compressed form is a littlelonger, i.e., preferably about 20 mm length. This does not constitute adrawback for its transcutaneous introduction and its positioning in theaortic orifice.

As mentioned above, the frame is strong enough to be able to oppose thepowerful recoil force of the distended valve and of the aortic annulus 2a. Preferably it does not possess any flexible properties. When theframe has reached its maximal expanded shape under the push of aforcefully inflated balloon, it remains substantially without anydecrease in size and without any change of shape. The size of the barsthat are the basic elements of the frame is calculated in such a way toprovide a substantial rigidity when the frame is fully expanded. Thesize of the bars and their number are calculated to give both maximalrigidity when expanded and the smallest volume when the metallic frameis its compressed position.

At the time of making the IV, the frame is expanded by dilatation to itsbroadest dimension, i.e., between 20 mm and 25 mm in diameter, so as tobe able to fasten the valvular structure on the inside side of itssurface. This fastening is performed using the techniques in current usefor the making of products such as other prosthetic heart valves ormultipolars catheters etc. Afterwards, it is compressed in its minimalsize, i.e., 4 or 5 mm, in diameter in view of its introduction in thefemoral artery. At time of the IV positioning, the frame is expandedagain by balloon inflation to its maximal size in the aortic orifice.

If the frame is built in an expanded position, it will be compressed,after fastening the valvular structure, by exerting a circular force onits periphery and/or on its total height until obtaining the smallestcompressed position. If the frame is built in its compressed position,it will be first dilated, for instance, by inflation of a balloon andthen compressed again as described above.

To help localizing the IV, the frame being the only visible component ofthe valve, the shaft of the balloon catheter on which will be mountedthe IV before introduction in the body (see below) possessespreferentially metallic reference marks easily seen on fluoroscopy. Onemark will be at level of the upper border of the frame and the other atthe level of the lower border. The IV, when mounted on the cathetershaft and crimpled on it, is exactly positioned taking into accountthese reference marks on the shaft.

Accordingly, the frame is visible during fluoroscopy when introduced inthe patient's body. When the frame is positioned at the level of theaortic annulus, the upper border of the frame is placed below thecoronary ostia. Furthermore, the implanting process during which theballoon inflation completely obstructs the aortic orifice, as seenbelow, is performed within a very short time, i.e., around 10 to 15seconds. This also explains why the frame is clearly and easily seen,without spending time to localize it. More particularly, its upper andlower borders are clearly delineated.

FIGS. 4 a and 4 b show an example of a preferred IV 13 of the presentinvention, respectively in its compressed position, in view of itsintroduction and positioning in the aortic orifice, and in its expandedand opened (systole) position. FIGS. 5 a and 5 b show the expandedposition of this example closed in diastole, respectively in perspectiveand in a crossed section view along the central axis XX of the valveprosthesis.

The valvular structure 14 is compressed inside the frame 10 when this isin its compressed position (FIG. 4 a), i.e., it fits into a 4 to 5 mmdiameter space. On the other hand, the valvular structure can expand(FIG. 4 b) and follow the frame expansion produced by the inflatedballoon. It will have to be able to reach the size of the inside of thefully deployed frame.

The illustrated IV 13 is made of a combination of two main parts:

-   -   1) the expandible but substantially rigid structure made of the        frame 10, a metallic frame in the example; and    -   2) a soft and mobile tissue constituting the valvular structure        14 exhibiting a continuous surface truncated between a base 15        and an upper extremity 16; the tissue is fastened to the bars 11        of the frame at its base 16 and is able to open in systole and        to close in diastole at its extremity 16, as the blood flows in        a pulsatile way from the left ventricle towards the aorta.

The tissue has rectilinear struts 17 incorporated in, it in planeincluding the central axis XX, in order to strengthen it, in particular,in its closed state with a minimal occupation of the space, and toinduce a patterned movement between its open and closed state. Otherexamples of strengthening struts are described below. They are formedfrom thicker zones of the tissue or from strips of stiffening materialincorporated in the tissue; they can also be glued or soldered on thevalvular tissue.

These strengthening struts help to prevent the valvular tissue fromcollapsing back too much and to evert inside the left ventricle throughthe base of the frame. These reinforcements of the valvular tissue helpmaintain the folded tissue above the level of the orifice duringdiastole, prevent too much folding back and risk of inversion of thevalvular structure inside the left ventricle. By also preventing toomuch folding, a decrease of the risk of thrombi formation can also beexpected by reducing the number of folds.

The truncated shape forming a continuous surface enables to obtain astrong structure and is more efficient for the systolo-diastolicmovements of the valvular tissue during heart beats. The truncoidalshape facilitates the closure of the valve structure at the beginning ofdiastole in facilitating the start of the reverse movement of thevalvular tissue towards its base at the time of diastole, i.e., at thetime of flow reversal at the very beginning of diastole. Duringdiastole, the valvular structure 14 thus fails down, folding on itself,thereby collapsing on its base, and therefore closing the aorticorifice. In fact, the valvular structure has preferably, as illustrated,an hyperboloid shape, with a curvature on its surface concave towardsthe aortic wall that will contribute to initiating its closure.

Moreover, the basis of the truncated hyperboloid is fixed on the lowerpart of a frame and the smallest extremity of the truncated hyperboloidis free in the blood stream, during the respected closing and openingphasis.

An important advantage of this hyperboloidal shape is that the upperextremity 16 of the valvular structure 14 can remain at a distance fromthe coronary ostia during systole as well as during diastole, because ofits smaller diameter, thus offering an additional security to makecertain that the passage of blood from aorta to the coronary ostia isnot impeded.

The base 15 of the truncated tissue is attached on the frame 10 along aline of coupling 18 disposed between the inferior fourth and the thirdfourth of the frame in the example. The upper extremity 16, with thesmaller diameter, overpasses the upper part of the frame by a fewmillimeters; 6 to 8 mm, for instance. This gives the valvular structurea total height of about 12 to 15 mm.

The upper extremity 16 of the truncated tissue, i.e., the smallerdiameter of the hyperboloidal structure 14, is about 17 to 18 mm indiameter (producing a 2.3 to 2.5 cm² area opening) for a 20 mm diameterbase of the truncated structure, or 19 to 20 mm in diameter (producing a2.8 or a 3 cm² area opening) for a 23 mm diameter base. An opening areaaround 2 cm² or slightly above, gives satisfactory results, particularlyin elderly patients who would not reasonably need to exert high cardiacoutput.

For instance, in the present example, the line of fastening of the baseof the truncated tissue on the frame will have to expand from a 12.5 mmperimeter (for a 4 mm external diameter of the compressed IV) to a 63 mmperimeter (for a 20 mm external diameter of the expanded IV), or to a 72mm perimeter (for a 23 mm external diameter, in case a 23 mm balloon isused).

Another advantage of this truncated continuous shape is that it isstronger and has less risk of being destroyed or distorted by theforceful balloon inflation at the time of IV deployment. Also, if thetruncated hyperboloidal shape is marked, for instance, with a 16 or 17mm diameter of the upper extremity as compared to a 20 mm diameter ofthe base (or 18 to 20 mm for 23 mm), the smaller upper part is compliantduring balloon inflation in order to enable the balloon to expandcylindrically to its maximal mm diameter (or 23 mm). This is madepossible by using a material with some elastic or compliant properties.

The valvular structure of the invention, as shown in the illustratedexample, includes advantageously a third part, i.e., the internal cover19 to be fixed on the internal wall of the frame 10. This internal coverprevents any passage of blood through the spaces between the bars 11 ofthe frame in case the implantable valve would be positioned with thefastening line of the valvular structure on the frame not exactly on theremains of the dilated aortic valve, i.e., either above or below. Italso strengthens the fastening of the valvular structure 14 to the frame10.

In the different sectional views of the different examples of IVaccording to the invention, as illustrated at FIGS. 6 a to 6 c, theinternal cover 19 covers the totality of the internal side of the frame10 (FIG. 6 a), only the lower part of the frame 10 (FIG. 6 b), or it canadditionally cover partially 3 to 5 mm as shown in the passage of bloodfrom aorta to the coronary ostia FIG. 6 c, the upper part defined abovethe coupling line 18 of the valvular structure.

For instance, such an extension of the internal cover 19 above thefastening line 18 of the valvular structure will give another securityto avoid any risk of regurgitation through the spaces between the bars11 in case the IV would be positioned too low with respect to the borderof the native aortic valve.

The internal cover can also be molded to the valvular structure orcasted to it which therefore constitutes an integral structure. Thevalvular structure and the internal cover are therefore strongly lockedtogether with minimum risk of detachment of the valvular structure whichis unceasingly in motion during systole and diastole. in that case, onlythe internal cover has to be fastened on the internal surface of theframe which renders the making of the IV easier and makes the completedevice stronger and more resistant. In particular, the junction of themobile part of the valvular structure and the fixed part being molded asone piece is stronger and capable to face the increasing movementsduring the systolo-diastolic displacements without any risk ofdetachment.

The presence of the internal cover makes an additional layer of plasticmaterial that occupies the inside of the frame and increases the finalsize of the IV. Therefore, in the case in which the internal cover islimited to the inferior part of the frame (that is, below the fasteningline of the valvular structure), it does not occupy any additional spaceinside the frame. Here also, it is more convenient and safer to make thevalvular structure and this limited internal cover in one piece.

In other aspects, to prevent any regurgitation of blood from the aortatowards the left ventricle during diastole, the base of the valvularstructure is preferably positioned exactly at the level of the aorticannulus against the remains of distorted stenosed valve pushed apart bythe inflated balloon. Therefore, there is no possibility of bloodpassage through the spaces between the metallic frame bars 11 below theattachment of the valvular structure.

However, to avoid any risk of leaks, the part of the frame below thefastening of the valvular structure (about 3 to 5 mm) is preferablycovered by an internal cover which is preferably made with the sametissue as the valvular structure. Thus, there would be no regurgitationof blood which is a possibility when there is any space between thevalvular structure fastened on the metallic frame and the line ofapplication of the frame on the aortic annulus. The internal cover makesa sort of “sleeve” below the fastening of the valvular structure on theinternal surface of the frame, covering the spaces between the framebars of the frame at this level, thus preventing any regurgitation ofblood through these spaces.

The internal cover can also have another function, i.e., it can be usedto fasten the valvular structure inside the frame, as described below.

At FIG. 6 d, the internal cover 19 is extended at its lower end 19′ toan external cover 19′ which is rolled up to be applied on the externalwall of the stent 10. The internal and external cover are molded, gluedor soldered to the bars of the stent 10.

The coupling process of the valvular structure on the frame is ofimportance since it has to be very strong without any risk of detachmentof the valvular structure from the frame during millions of heart beatswith pulsatile blood flow alternatively opening and closing the valvularstructure.

The valvular structure of the invention folds to a very small sizeinside the frame in the compressed position of the valve and isexpandable up to 20 to 23 mm diameter. Also, the valvular structure canresist the strong force exerted by the maximally inflated balloon thatwill powerfully squeeze it against the bars of the frame or against theinternal cover, this one being squeezed directly against the bars of theframe. The junction zone is also particularly subjected to very strongpressure exerted by the inflated balloon. Furthermore, this junctionzone must not tear or break off during expansion of the balloon. At thistime, each part of the junction zone is squeezed against the bars butnonetheless follows the expansion of the frame.

As shown in FIG. 7, the junction zone is, for example, a fastening line20 which follows the design of a “zig-zag” line drawn by theintercrossing bars 11 of the frame on the internal cover 19.

The fastening of the valvular structure to the frame can be made bysewing the internal and/or the external cover to the bars. To preventany leakage of blood, stitches are preferably numerous and very close toeach other, either as separated stitches or as a continuous suture line.Also, the stitches are made directly around the bars 11. Furthermore,since the valvular structure is expanded together with the metallicframe, the stitches, if made as a continuous suture line, are also ableto expand at the same time.

The fastening process can also be made by molding the base of thevalvular structure on the frame. At this level, the bars 11 are imbeddedin the coupling line of the valvular structure 14. This mold way alsoconcerns the internal cover 19, when it goes below the coupling line 14on the frame over few millimeters, for example, 2 to 4 mm. As mentionedabove, this is intended in order to prevent any regurgitation of bloodjust below the lower part of the valvular structure 14 in case the frame10 would not be exactly positioned on the aortic annulus but at fewmillimeters away.

The fastening process can further be made by gluing or soldering thevalvular structure on the bars with sufficiently powerful biocompatibleglues. The same remark can be made concerning the internal cover of theframe below the coupling line of the valvular structure.

Also, this allows the coupling line to follow the frame changes from thecompressed position to its expanded one.

The valvular structure can also be fastened on the internal coverpreviously fixed at the total length of the internal surface of themetallic frame. The internal cover constitutes therefore a surface onwhich any type of valvular structure be more easily sewed, molded orglued. Because it is a structure with a large surface and is notinvolved in the movements of the valvular tissue during systole anddiastole, the internal cover is more easily fastened to the internalsurface of the frame.

In the particular embodiment shown in FIGS. 8 a and 8 b, the internalcover 19 is fastened, after introduction (indicated by the arrow B), atthe upper and lower extremities of the frame 10 on the upper and lowerzig-zag lines of the intercrossing bars 11. In fact, the fastening ofthe internal cover 19 on the zig-zag lines made by the intercrossingbars 11 of the frame allows an easier passage of blood from the aortaabove the IV towards the coronary ostia. Indeed, the blood can find morespace to flow into the coronary ostia by passing through the lowestpoint of each triangular space made by two intercrossing bars 11, asindicated by the arrows A1 (see also Figure Ib).

The fastening of the internal cover 19 on the extremities can bereinforced by various points of attachment on various parts of theinternal surface of the frame 10. The internal cover 19 can be fastenedby sewing, molding or gluing the bars 11 onto the frame.

Fastening the valvular tissue (and the cover tissue below) on the insideof the frame, requires work on the frame in its expanded position tohave access to the inside of this cylindric frame. In a preferredembodiment the frame is expanded a first time for fastening the valvulartissue on its bars, then compressed back to a smaller size to be able tobe introduced via arterial introducer and finally expanded again by theballoon inflation.

Since it is aimed at being positioned in the heart after having beenintroduced by a catheterization technique by a transcutaneous route in aperipheral artery, mainly the femoral artery, the IV should preferablyhave the smallest possible external diameter. Ideally, it should be ableto be introduced in the femoral artery through a 14 F (4.5 mm) sizearterial introducer which is the size of the arterial introducercommonly used to perform an aortic dilatation. However, a 16 F (5.1 mm)or even a 18 F (5.7 mm) introducer would also be acceptable.

Above this size, the introduction of the IV in the femoral artery shouldprobably be done by a surgical technique. This is still quite acceptablesince the surgical procedure would be a very light procedure which couldbe done by a surgeon with a simple local anaesthesia. It has to berecalled that this technique is used to position big metallic frames,about 24 F in size (7.64 mm in diameter), in the abdominal aorta for thetreatment of aneurysms of the abdominal aorta. In that situation, thisnecessitates surgical repair of the artery after withdrawal of thesheath (M. D. Dake, New Engl. J. Med. 1994;331:1729-34).

Ideally, an IV should be able to last several tenths of life yearswithout defect, like the mechanical prosthetic valves which arecurrently implanted by the surgeons. Nevertheless, an implantable valvethat would last at least ten years without risk of deterioration wouldbe effective for the treatment of elderly patients.

A valvular structure according to the invention is made of a supple andreinforced tissue which has a thickness to be thin enough to occupy asless as possible space in the compressed form of the valve, is pliable,and also strong enough to stand the unceasing movements under the bloodpressure changes during heart beats. The valvular structure is capableof moving from its closed position to its open position under the actionof the force exerted by the movements of the blood during systole anddiastole, without having any significant resistance to blooddisplacements.

The material used for the tissue, which exhibits the above mentionedrequirements, may be TEFLON® or DACRON®, which are quite resistant tofolding movements, at least when they are used to repair cardiac defectssuch as inter-atrial or interventricular defects or when they are usedto repair a valve such as the mitral valve which is subjected to highpressure changes and movements during heart beats. Also, a main point isthe increasing systolo-diastolic movements of the valvular tissue,particularly at its junction with the rigid part of the IV, and it istherefore necessary to find the most possible resistant material tissue.

As mentioned previously, the valvular structure can also possibly bemade with biological tissue such as the pericardium, or with porcineleaflets, which are commonly used in bioprosthetic surgically implantedvalves.

Moreover, the valvular prosthesis of the present invention does notinduce any significant thrombosis phenomenon during its stay in theblood flow and is biologically neutral.

To prevent the risk of thrombus formation and of emboli caused by clots,a substance with anti-thrombic properties could be used, such asheparine, ticlopidine, phosphorylcholine, etc., either as a coatingmaterial or it can be incorporated into the material used for theimplantable valve, in particular, for the valvular structure and/or forthe internal cover.

The valvular structure of the invention can have several types ofdesigns and shapes. Besides the example illustrated in FIGS. 4 and 5,examples of strengthened valvular structures according to the inventionare shown in FIGS. 9 to 11, respectively in the closed (FIGS. 9 a, 10 a,11 a) and in the open state (FIGS. 9 b, 10 b, 11 b) to form a prostheticvalve according to the present invention. In those figures, the frameline is simplified to clarify the drawings.

To help initiate and finalize the closure of the valvular structure,four strengthening struts 14 a are slightly inclined from the base tothe upper part as compared to the central axis XX of the structure, asshown in FIGS. 9 a and 9 b. Accordingly, a patterned movement of thevalvular structure, during the closing and the opening phases, isinitiated. This patterned movement is, in the present case, anhelicoidal-type one, as suggested in FIGS. 9 b and 10 b by the circulararrow 21.

FIGS. 10 a and 10 b illustrate another embodiment to help the closing ofthe valvular structure and which also involves an helicoidal movement.Represented by lines 22, inclined pleats are formed in the tissue toimpart such a movement. As illustrated, these lines have an inclinationfrom the base to the upper part of the valvular structure tissue 14.Pleats are formed by folding the tissue or by alternating thinner andthicker portions. The width and the number of those pleats are variable,and depend particularly on the type of material used. According toanother example, these pleats 22 are combined with the above describedinclined strengthening struts.

These reinforcing pleats and/or struts, rectilinear or inclined, havethe advantage to impart a reproducible movement and, accordingly, toavoid the valvular structure from closing to a nonstructurized collapseon the frame base.

Another shape of the valvular structure comprises two portions: oneportion being flexible but with some rigidity, having a rectangularshape, occupying about one third of the circumference of the valvularstructure, and the other portion being more supple, flexible andfoldable occupying the rest of the circumference at its base as well asat its upper, free border. According to FIG. 11 c, this valve is opened,during the ejection of blood, i.e., during systol. In FIG. 11 d, a frontview of the valve is closed, during an intermediate diastole, and inFIG. 11 e the same closed valve during diastole is shown from a sideview. The semi-rigid part 24′ moves little during systole and duringdiastole. The foldable part 23′ moves away from the rigid part duringsystole to let the blood flow through the orifice thus made. Thisorifice, due to the diameter of the upper part which is the same as thatof the open stent, is large, generally as large as that of the openstent. At the time of diastole, due to the reverse of pressure, thefoldable part moves back towards the semi-rigid part and presses on it,and thus closes the orifice and prevents any regurgitation of blood.

The advantage of such a valve design is to allow a large opening of theupper part of the valvular structure, not only to permit more blood flowat time of systole after the valve has been implanted, but also at thevery time of implantation, when the balloon is maximally inflated toexpand the valve to imbed it in the valvular annulus. The diameter ofthe upper part of the valvular structure could be the same size as theballoon, so that there would be no distension of the valvular part ofthe valve at the time of implantation, and therefore no risk ofdeterioration of the valvular structure by the inflated balloon.

The foldable part of the valve could be reinforced by strengtheningstruts to prevent an eversion of the valve towards the left ventricleduring diastole.

Another shape of the valvular structure, as illustrated in FIGS. 11 aand 11 b comprise four portions, alternatively a main portion 23 and amore narrow portion 24. The main and the narrow portions are facing eachother. Each portion has an isosceles trapezoidal shape. The mainportions 23 are flexible but with some slight rigidity and the morenarrow portions 24 are compliant, more supple and foldable. In this typeof design, the two slightly rigid main portions 23 maintain the valvularstructure closed during diastole by firmly applying on each other intheir upper extremities, thus forming a slot-like closure 25. Thisparticular embodiment needs less foldable tissue than in the previousembodiments and the closure of the valvular structure at the time ofearly diastole does not have any tendency to collapse towards the aorticannulus.

Another design for the valvular structure is a combination of acylindrical shape followed by a truncated shape.

This type of valvular structure is longer that the hyperboloidal type,for instance, 25 or 30 mm long, therefore exceeding out of the upperpart of the metallic frame, by 10 to 20 mm. The cylindrical partcorresponds to the I0 metallic frame and remains inside it. Thetruncated conic shape is the upper part of the valvular structure,totally exceeding out of the upper extremity of the metallic frame. Anadvantage of such a design is that the balloon can be inflated only inthe cylindrical part of the valvular structure, therefore without riskof stretching the truncated conical part of the upper diameter which issmaller than that of the inflated balloon.

When the upper extremity of the cylindrical part has the same size asthe lower extremity, there is no difference during balloon inflation inthe degree of force exerted by the balloon on the lower and on the upperextremity of the valvular structure. Preferably, rectilinear reinforcingstruts are used in this embodiment, to strengthen the valve structureand aid in its shutting without collapsing and inverting inside the leftventricle through the aortic annulus under the force of the diastolicpressure.

Two different processes for implanting a valve according to the presentinvention are shown respectively in FIGS. 13 a to 13 l with a uniqueballoon catheter, as illustrated in FIGS. 12 a and 12 b and in FIGS. 15a to 15 f, with a two-balloon catheter, as illustrated in FIG. 14.

The IV positioning in the aortic orifice and its expansion can beperformed with the help of a unique substantially cylindrical ballooncatheter 26 in the so-called unique-balloon catheterization technique.

Preparing for its introduction by transcutaneous route in the femoralartery, the IV 13 is, as illustrated in the perspective view of FIG. 10a in a compressed form crimpled on the balloon catheter 26. A centralsectional view of the mounted IV 13 on the complete balloon catheter 26is shown in FIG. 12 b.

The shaft 27 f of the balloon dilatation catheter 26 is as small aspossible, i.e., a 7F (2.2 mm) or a 6 F (1.9 mm) size. The balloon 26 ismounted on the shaft 27 between two rings R. Moreover, the shaft 27comprises a lumen 28 (FIG. 12 b) as large as possible for inflation ofthe balloon 26 with diluted contrast to allow simple and fast inflationand deflation. It has also another lumen 29 able to accept a stiff guidewire 30, for example 0.036 to 0.038 inches (0.97 mm), to help positionthe implantable valve with precision.

The balloon 26 has, for example, a 3 to 4 cm length in its cylindricalpart and the smallest possible size when completely deflated so that itwill be able to be placed inside the folded valve having an outsidediameter which ranges between about 4 and 5 mm. Therefore, the foldedballoon preferably has at the most a section diameter of about 2.5 to 3mm.

The balloon is therefore made of a very thin plastic material. It isinflated with saline containing a small amount of contrast dye in such away to remain very fluid and visible when using X-ray.

However, the balloon 26 has to be sufficiently strong to resist the highpressure that it has to withstand to be capable of expanding the foldedvalvular structure 14 and the compressed frame in the stenosed aorticorifice considering that, although pre-dilated, the aortic orifice stillexerts a quite strong resistance to expansion because of the recoilphenomenon.

This procedure is shown in FIGS. 13 a to 13 e.

In contrast to the technique used when performing the usual aorticdilatation (without valve implantation), i.e., inflating the balloonmaximally markedly above the nominal pressure, if possible, up to thebursting point (which occurs always with a longitudinal tear, withoutdeleterious consequence, and with the advantage of both exerting amaximal dilating force and restoring blood ejection instantaneously),the balloon inflated for expansion of an implantable valve should notburst in any case. Indeed, bursting of the balloon would involve a riskof incomplete valve expansion and wrong positioning. Therefore, theballoon should be very resistant to a very high pressure inflation.Furthermore, the balloon is inflated only up to the nominal pressureindicated by the maker and the pressure is controlled during inflationby using a manometer. Such relatively low pressure should be sufficientsince prior to positioning the IV, an efficacious dilatation of thestenosed aortic valve according to the usual technique with a maximallyinflated balloon for example 20 mm or 25 mm in size in such a way tosoften the distorted valvular tissue and facilitate the enlargement ofthe opening of the valve at time of IV implantation is performed.

The implantation of the aortic valve 20 can be made in two steps, asdescribed as follows.

The first step, as shown in FIGS. 13 a to 13 f, consists in introducingthe shaft 27 and balloon catheter 26 along the guide wire previouslypositioned in the ventricle 4 (FIGS. 13 a-13 b). The dilatation of thestenosed aortic valve 1′, 2′ using a regular balloon catheter, accordingto the commonly, performed procedure, i.e., with the guide wire 30introduced in the ventricle 4 (FIG. 13 a) and with maximal inflation ofthe balloon 26 (FIGS. 13 c to 13 d) up to the bursting point. Dilatationis performed at least with a balloon having about 20 mm diameter, but itcan be performed with a balloon having about 23 mm diameter so as toincrease maximally the aortic orifice opening before implantation of thevalve although the implantable valve is about 20 mm in diameter. Thispreliminary dilatation of the aortic orifice helps in limiting the forcerequired to inflate the balloon used to expand the implantable valve andposition it in the aortic orifice, and also in limiting the recoil ofthe aortic valve that occurs immediately after balloon deflation. Theballoon is deflated (FIG. 13 a) and pulled back on the wire guide 30left inside the ventricle.

Owing to the marked recoil of the stenosed valve and also of the strongaortic annulus, the 20 mm diameter valve is forcefully maintainedagainst the valvular remains at the level of the aortic annulus.Preliminary dilatation has another advantage in that it permits aneasier expansion of the IV, having a lower pressure balloon inflationwhich helps prevent damage of the valvular structure of the IV. Thisalso facilitates the accurate positioning of the prosthetic valve.

The second step corresponds to the implantation of the valve 13 is shownin FIGS. 13 g to 13 l. The positioning of the IV needs to be precise ata near 2 or 3 mm, since the coronary ostia 6 has to remain absolutelyfree of any obstruction by the valve 13 (FIGS. 13 k and 13 l). Asmentioned above, this is, for example, performed with the help of theimage of the sus-valvular angiogram in the same projection fixed on anadjacent TV screen. The expansion and the positioning of the valveprosthesis 13 is performed within a few seconds (15 to 20 among at most)since during the maximal balloon inflation (which has to be maintainedonly a very few seconds, 3, 4,) the aortic orifice is obstructed by theinflated balloon 31 and the cardiac output is zero (FIG. 13 h). As forthe pre-dilatation act itself, the balloon 26 is immediately deflatedwithin less than 5 or 6 seconds (FIG. 13 j) and, as soon as thedeflation has clearly begun, the closing and opening states of the IVare active whereas the balloon is pulled back briskly in the aorta(FIGS. 13 j to 13 l). In case the IV is not maximally expanded by thefirst inflation, it is possible to replace the balloon inside the IV andto reinflate it so as to reinforce the expansion of the IV.

The IV 13 can also be used in aortic regurgitation. This concerns moreoften younger patients rather than those with aortic stenosis. Thecontraindication to surgical valve replacement is often not due to theold age of the patients, but stems mainly from particular cases wherethe general status of the patient is too weak to allow surgery, orbecause of associated pathological conditions. Apart from the fact thatthere is no need for a preliminary dilatation, the procedure of thevalve implantation remains approximately the same. The balloon inflationinside the IV is chosen accordingly, taking also into account the factthat it is necessary to overdilate the aortic annulus to obtain a recoilphenomenon of the annulus after balloon deflation to help maintain theIV in position without any risk of displacement.

However, the size of the expanded implantable valve is around 25 to 30mm in diameter, or even bigger, because the aortic annulus is usuallyenlarged. A preliminary measurement of the annulus will have to beperformed on the sus-valvular angiography and by echocardiography todetermine the optimal size to choose.

The IV can be used in the mitral position, mainly in case of mitralregurgitation, but also in case of mitral stenosis. Here again, the IV20 is only described when used only in cases of contraindication tosurgical valve repair or replacement. The procedure is based on the samegeneral principles though the route for the valve positioning isdifferent, using the transseptal route, like the commonly performedmitral dilatation procedure in mitral stenosis. The IV size is quitelarger than for the aortic localization (about 30 to 35 mm in diameterwhen expanded or clearly above in case of a large mitral annulus, afrequent occurrence in mitral insufficiency), to be capable of occupyingthe mitral area. A preliminary measurement of the mitral annulus isperformed to determine the optimal implantable valve size to choose.Since the introduction of the IV is performed through a venous route,almost always through the femoral vein which is quite large anddistensable, the bigger the size of the IV in its compressed position isnot a drawback even if the diameter size is about 6 or 7 mm. Moreover,the problem of protection of the coronary ostia as encountered in theaortic position does not exist here which therefore makes the procedureeasier to be performed.

Finally, the IV can be used to replace the tricuspid valve in patientswith a tricuspid insufficiency. This procedure is simple to performsince the positioning of the IV is made by the venous route, using theshortest way to place in the right position at the level of thetricuspid orifice practically without any danger from clot migrationduring the procedure. A large implantable valve is used, with a diameterof about 40 mm or even larger because the tricuspid annulus is oftenmarkedly dilated in tricuspid insufficiency. Here also, as in the mitralposition, the compressed IV and the catheter used can be withoutinconvenience, quite larger than that for the aortic position because ofthe venous route used.

Furthermore, it has to be noted that the IV can be used also as a firststep in the treatment of patients who have contraindication to surgery,when they are examined for the first time, but who could improve lateron after correction of the initial hemodynamic failure. The IV procedurecan be used as a bridge towards surgery for patients in a weak generalcondition which are expected to improve within the following weeks ormonths after the IV procedure in such a way that they can be treated byopen heart surgery later on. In the same vein, the IV procedure can beused as a bridge towards surgical valve replacement or repair inpatients with a profoundly altered cardiac function that can improvesecondarily owing to the hemodynamic improvement resulting from thecorrection of the initial valvular disease by the IV implantation.

Another technique for implantation of an aortic valve by transcutaneouscatheterization uses a two-balloon catheter.

An example of this technique using the two parts IV with a two-ballooncatheter 40 is shown in FIG. 14.

Two-balloons 26 and 26′ are fixed on a unique catheter shaft 27, saidballoons being separated by a few millimeters. The two balloons arepreferably short, i.e., about 2 to 2.5 cm long in their cylindricalpart. The first balloon 26 to be used, carries a first frame 10 aimed atscaffolding the stenosed aortic orifice after initial dilatation. Thisfirst balloon 26 is positioned on the aorta side, above the secondballoon 26′ which is positioned on the left ventricle side. The secondballoon 26′ carries the expandable valve 13 which is of the typedescribed above made of a second frame 10′ and a valvular structure 14attached to said frame 10′. The difference is that the second frame doesnot need to be as strong as the first frame and is easier to expand withlow balloon pressure inflation which does not risk damaging the valvularstructure 14.

This enlarges the choice for making a valvular structure without havingto face two contradictory conditions:

-   -   having a soft and mobile valvular structure 14 capable of        opening and closing freely in the blood stream without risk of        being damaged by a balloon inflation; and    -   needing a reinforced frame strong enough to be capable of        resisting without any damage, a strong pressure inflation of the        expanding balloon.

The shaft 27 of this successive two-balloon catheter 40 comprises twolumens for successive and separate inflation of each balloon. Indeed, anadditional lumen capable of allowing a fast inflation occupies space inthe shaft and therefore an enlargement of the shaft is necessary.However, this enlargement of the shaft stops at the level of the firstballoon 26 since, further to said first balloon, only one lumen isnecessary to inflate the second balloon 2C, at the level of the IV whichis the biggest part of the device.

Another advantage of this two part IV with a two-balloon catheter isthat each set of implantable valve and balloon has a smaller externaldiameter since each element to be expanded, considered separately, issmaller than in combination. This allows obtaining more easily a finaldevice with an external diameter 14F.

The first balloon is sufficiently strong to avoid bursting even at avery high pressure inflation. This first balloon is mounted in the framein its deflated position, prior to its introduction by the strong framewhich is aimed to scaffold the dilated stenosed aortic valve. The sizeand shape of said frame is comparable to what has been describedpreviously but said frame is calculated (in particular the material, thenumber and diameter of its bars are chosen by the person skilled in theart) to make sure that it will resist the recoil of the dilated valveand that it will be securely embedded in the remains of the nativeaortic valve.

The second balloon does not need to be as strong as the first one and,therefore, can be thinner, occupying less space and being easier toexpand with a lower pressure for balloon inflation. This second balloon26′ is mounted in the valve itself which, as in the precedingdescription, comprises a frame to support the valvular structure andsaid valvular structure.

Also, the second frame 10′ does not need to be as strong as the firstone. This frame can be slightly shorter, 10 mm instead of 12 mm, and itsbars can be thinner. This frame can have an external surface which is abit rough to allow better fixation on the first frame when expanded. Thebars may also have some hooks to fasten to the first frame.

The valvular structure is attached on said second frame and expanded byrelatively low pressure in the second balloon called hereafter the IVballoon. It does not need to be as strong as in the preceding case (IVin one part and unique balloon catheter technique) and, therefore, itoccupies less space and has less risk to be damaged at the time ofexpansion.

This technique is shown in FIGS. 15 a to 15 f.

One of the problems relevant to the IV implantation procedure asdescribed above, with the IV in one part, is the expansion at the sametime by the same balloon inflation of both the frame and the valvularstructure. Indeed, the frame is a solid element and the valvularstructure is a relative weak one that could be damaged when squeezed bythe inflated balloon.

Therefore, the valve implantation can be performed in two immediatelysuccessive steps. The first step (FIGS. 15 a-15 b) corresponds to theexpansion and the positioning of the first frame with the first balloon26 wherein inflation is performed at a high pressure. The second step(FIGS. 15 d-15 e) corresponds to the expansion and the positioning ofthe valvular structure 14 inside the frame 10′ using the second balloon2C. This second step follows the first one within a few seconds because,in the time interval between the two steps, there is a total aorticregurgitation towards the left ventricle which is an hemodynamiccondition that cannot be maintained for more than a few heart beats,i.e., a few seconds, without inducing a massive pulmonary edema and adrop to zero of the cardiac output.

In another embodiment, the first frame to be introduced comprises thevalvular structure and the second frame being stronger than the firstone to scaffold the previously deleted stenosed aortic valve.

The advantage of this two step procedure would be to allow expansion andpositioning of the frame part 10′ of the R 13 using strong pressureinflation of the balloon 26′ without the risk of damaging the valvularstructure 14 which, for its own expansion, would need only lightpressure inflation.

The method is schematically detailed in FIGS. 15 a to 15 f. A previousdilatation of the stenosed aortic valve is performed as an initial stepof the procedure to prepare the distorted valve to facilitate thefollowing steps:

-   -   1/ positioning the double balloon catheter 40 with the first        balloon 26 with the frame at the level of the aortic annulus 2        a, the second IV balloon 26′ being inside the left ventricle        beyond the aortic annulus 2 a (FIG. 15 a);    -   2/ compression of the stenosed aortic valve 1′, 2′ with the        first balloon 26 having a 20 mm, preferably with a 23 mm        diameter, the balloon being inflated maximally up to the        bursting point, to prepare the IV insertion (FIG. 15 b).        Inflation lasts a few seconds (preferably 10 seconds at most)        with powerful pressure being used to expand the frame and        forcefully embed said frame in the remains of the dilated valve;    -   3/ an immediate speedy deflation of said first balloon 26        follows (FIG. 15 c); as soon as the balloon 26 is beginning to        clearly deflate, the first frame 10 remaining attached to the        stenosed valve 1′, 2′, the catheter is withdrawn to position the        IV balloon 26′ inside the previously expanded frame 26 (FIG. 15        c in which the frame 10′ is partially drawn for clarity        purpose); and    -   4/ immediately after being well positioned, the IV balloon 26′        is promptly inflated, to expand the IV 13 (FIG. 15 c); and /        when the IV 13 is blocked inside the first frame 10, the IV        balloon 26′ is deflated (FIG. 18 f).

Finally, the whole device has to be withdrawn to allow homeostasis ofthe femoral artery puncture hole.

The total duration of the successive steps, particularly the time duringwhich the balloons are inflated, and the time during which the frame isexpanded whereas the valve has not yet been positioned and expanded, isabout 20 to 30 seconds. This is feasible if the balloons are inflatedand deflated within very a few seconds, 6 to 8, for instance. This ispermitted if the lumen of the shaft can be sufficiently large, takinginto account the inescapable small diameter size of the shaft. This canalso be facilitated by a device producing instantaneously a stronginflation or deflation pressure.

1. A method for treating a native aortic valve in a human heart,comprising: advancing an expandable member to a position within thenative aortic valve, the native aortic valve having at least twovalvular leaflets; dilating the native aortic valve by expanding theexpandable member to push aside the valvular leaflets of the nativeaortic valve; collapsing the expandable member and withdrawing theexpandable member from the native aortic valve; advancing a prostheticvalve to a position within the dilated native aortic valve, theprosthetic valve being radially compressed during the advancement; andradially expanding the prosthetic valve within the dilated aortic valve,wherein the expanded prosthetic valve maintains the native aortic valvein the dilated condition and replaces the valvular function of thenative aortic valve.
 2. The method of claim 1, wherein the prostheticvalve is advanced percutaneously through the aorta in a retrogradedirection.
 3. The method of claim 1, wherein the prosthetic valvecomprises a metallic frame and a valvular structure coupled to theframe.
 4. The method of claim 3, wherein the valvular structurecomprises biological tissue.
 5. The method of claim 3, wherein themetallic frame is viewed under fluoroscopy during advancement of theprosthetic valve toward the native aortic valve.
 6. The method of claim3, wherein the metallic frame engages the valvular leaflets of thenative aortic valve.
 7. The method of claim 6, wherein the prostheticvalve is positioned such that valvular leaflets provide a stable basefor fixing the metallic frame within the native aortic valve.
 8. Themethod of claim 7, wherein the valvular leaflets recoil inward afterdilatation to further contribute to the fixation of the metallic frame.9. The method of claim 3, wherein the metallic frame is made of steel.10. The method of claim 3, wherein the metallic frame has a heightbetween about 10 and 15 millimeters in the radially expanded condition.11. The method of claim 3, wherein the metallic frame has a top end anda bottom end and wherein the top end of the frame is located below thecoronary ostia after the prosthetic valve is expanded such that thecoronary ostia remain free of obstruction from the prosthetic valve. 12.The method of claim 11, wherein the bottom end of the frame is locatedabove the mitral valve in the human heart after the prosthetic valve isexpanded such that the mitral valve remains free of obstruction from theprosthetic valve.
 13. The method of claim 1, wherein the native aorticvalve is dilated to a diameter of at least about 20 millimeters beforeadvancing the prosthetic valve.
 14. A method for treating a native valvein a human heart, comprising: advancing an expandable balloon to aposition within the native valve, the native valve having at least twovalvular leaflets; dilating the native valve by inflating the balloon topush aside the valvular leaflets; deflating the balloon and withdrawingthe balloon from the native valve; advancing an expandable prostheticvalve to a position within the dilated native valve, the prostheticvalve including a valvular structure coupled to an expandable frame; andradially expanding the prosthetic valve within the dilated native valve,wherein an outer surface of the expandable prosthetic valve engages theleaflets of the native valve and the expandable prosthetic valvereplaces the function of the native valve.
 15. The method of claim 14,wherein the valvular structure has a truncated shape.
 16. The method ofclaim 15, wherein the valvular structure has a hyperboloid shape. 17.The method of claim 14, wherein the frame is manufactured in an expandedcondition and the valvular structure is coupled to the frame while theframe is in the expanded condition and further comprising compressingthe frame and valvular structure before advancement toward the dilatednative valve.
 18. The method of claim 14, wherein the native valve is amitral valve and the prosthetic valve is advanced percutaneously using atransseptal route.
 19. The method of claim 18, wherein the prostheticvalve has an expanded diameter of at least about 30 millimeters.
 20. Amethod of implanting a prosthetic valve in a heart for treating valvularaortic stenosis, comprising: providing a first elongate catheter havingan expandable balloon disposed along a distal end portion thereof;positioning the balloon within an aortic valve by manipulation of thefirst elongate catheter; expanding the balloon to dilate the aorticvalve; collapsing the balloon and withdrawing the first elongatecatheter through the aorta; providing a second elongate catheter havingan expandable prosthetic valve disposed along a distal end portionthereof; advancing the second elongate catheter through the aorta towardthe dilated aortic valve; deploying the prosthetic valve within thedilated aortic valve; and withdrawing the second elongate catheterthrough the aorta.